Generally, there are three industrial methods for producing titanium boride in industry:
(1) Direct reaction of metal titanium and element boron at high temperature: Ti+2B═TiB2;
(2) Boron carbide method: direct reaction of titanium dioxide and boron carbide in a carbon tube at the presence of C:
2TiO2+B4C+3C=2TiB2+4CO, the reaction temperature is within a range from 1800° C. to 1900° C. if the carbon tube is under the atmosphere of H2; and the reaction temperature can be lowered to be within a range from 1650° C. to 1750° C. if the carbon tube is under vacuum;
(3) vapor deposition method: with TiCl4 and BCl3 as feedstock, the reaction below is performed under the participation of H2:
TiCl4+BCl3+5H2=TiB2+10HCl; the deposition temperature is within a range from 8000° C. to 1000° C., and abrasive-grade and electronic-grade products can be manufactured.
The three preparation methods above have the following features in common: high reaction temperature, strict reaction conditions, typically less than 90% of reaction yield, and high comprehensive preparation cost.
The method for preparing sodium fluoroaluminate (sodium cryolite) in industry is typically synthesis method: anhydrous hydrofluoric acid reacts with aluminum hydroxide to generate fluoaluminic acid, which then reacts with sodium hydroxide at high temperature, and fluoroaluminate product is prepared after filtering, drying, melting and crushing; the reactions are as follows: 6HF+Al(OH)3=AlF3.3HF+3H2O and AlF3.3HF+3NaOH═Na3AlF6+3H2O; the sodium fluoroaluminate, which is synthesized using such a method, has a relative molecular weight of 209.94 and a molecular formula of AlF3.mNaF (m=3.0). The sodium cryolite prepared using the current industrial synthesis methods generally has a molecular ratio m between 2.0 and 3.0, so it is difficult to prepare pure low-molecular-weight sodium cryolite having a molecular ratio m between 1.0 and 1.5.